Fire resistant thermoplastic pallet

ABSTRACT

The presently disclosed thermoplastic pallet advantageously incorporates fire resistance by virtue of one or more of the following aspects: a sprinkler friendly deck or frame; variable fire retardant or coating distributions; fire collapsible cross beams; foam filled or foam coated parts; and pallet design, including proportioning amounts of plastic and metal utilized in construction. Exemplary combinations of features enables the pallet to meet all the dimensional, mechanical behavior and burn test requirements. The use of metal components including a corrugated aluminum deck having specially position through holes for sprinkler water, and the engineered placement of hollows in the structural plastic parts enables a reduction in the amount of plastic, and the amount of fire retardant in what plastic there is and in the pallet as a whole.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationNos. 60/657,484, filed Mar. 1, 2005; 60/657,678, filed Mar. 1, 2005;60/657,488, filed Mar. 1, 2005, U.S. patent application Ser. No. (numbernot assigned), filed Feb. 18, 2008, entitled “Fire Sprinkler FriendlyPallet”, which claimed priority to U.S. Provisional Patent ApplicationSer. No. 60/654,764, filed Feb. 18, 2005, and U.S. patent applicationSer. No. (number not assigned), filed Feb. 18, 2005, entitled “FireCollapsible Cross Beamed Pallet”, which claimed priority to U.S.Provisional Patent Application Ser. No. 60/654,759, filed Feb. 18, 2005,and is a continuation-in part of U.S. patent application Ser. No.10/729,615, filed Dec. 5, 2003, which is a divisional of U.S. patentapplication Ser. No. 09/938,954, filed Aug. 24, 2001, now U.S. Pat. No.6,705,237, which claimed priority to U.S. Provisional Patent ApplicationSer. No. 60/227,537, filed Aug. 24, 2000, the entire contents of each ofwhich are specifically incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a device for the transportation of packagedgoods, and, more particularly, to a pallet that meets certain standardsset by the Grocery Manufacturers Association (GMA) and others forweight, durability, and strength.

BACKGROUND

Pallets, both bearing goods and empty, are often stored on racks inwarehouses which are fitted with fire-fighting automatic sprinklersystems. The heat and rate of combustion of the pallets made of typicalpolyethylene or polypropylene pallet material are inherently highcompared to traditional wood pallets. A bad conflagration can result,overwhelming the sprinkler system of a typical warehouse, many of whichwere designed for wood pallets. Adding additional sprinkler systems, orhaving special areas for plastic pallets, involves substantial unwantedcosts or logistics problems.

A criteria which is used to evaluate plastic pallets is to compare theirperformance to wood pallets, to find if they perform equal or betterthan wood pallets under fire conditions. In particular, UnderwritersLaboratories (Northbrook, Ill., U.S.) has developed a Standard, UL 2335,“Classification Flammability of Plastic Pallets”. The Standard isconsistent with U.S. National Fire Protection Association (NFPA)Standards 231 and 231C, which relate to warehouses and rack (pallet)storage of materials in warehouses. Under the UL Standard, a group ofstacked pallets is artificially ignited in a certain defined containmentbuilding. Measurements are made of the rate of spread of a fire within astack of pallets, the amount of heat released during burning of thestack (gauged by the number of standard sprinkler heads which aretriggered in the test setup), and the structural stability (resistanceto collapse) of the stack.

Plastic pallets have been in use, but have not gained wide acceptance,since they have not met all the criteria for pallets. Generally, palletsmust have certain dimensions, be strong enough to carry specified loads,must not be too heavy, and must be durable in resisting damage duringuse, as measured by certain tests and field use. In particular, to beaccepted, they must meet standards of the Grocery Manufacturers ofAmerica (GMA). Among the criteria in the standard are that pallets havefire resistances, sufficient to not exceed the heat release set byUnderwriters Lab Standard 2335 when intentionally set on fire in a testfacility, to simulate a warehouse fire. The pallet also must not be tooheavy, must be strong enough to carry specified loads, and must bedurable in resisting damage during use, as measured by certain tests andfield use. So far, no pallet has been able to meet all these criteria.Indeed, the more fire retardant included in the plastics, the morefragile the plastic. Thus, other approaches are sought. And of course,cost is important. It has been a stumbling block for pallets to meet theforegoing mechanical and cost criteria to also meet fire resistancestandards. One accepted criterion is that, pallets in a rack, subjectedto a fire test which simulates a warehouse fire, cannot burn in a waysuch that they exceed the maximum heat release (heat of combustion inany 10 minute time span) set by Underwriters Lab Standard 3435.

One solution may appear to be making pallets out of fire resistingplastics, such as Noryl plastic for pallets described and offered byGeneral Electric Co., or such as polypropylene or polyethylenecontaining significant amounts of fire retardants. However, taking thatapproach that creates several problems. They variously includeadditional weight, reduced strength, the toxicity and environmentalunacceptability of many of the good fire retardant additives, andincreased cost.

What is needed in the art is a low cost, low weight, durable, fireresistant pallet.

SUMMARY

The above-described and other problems and disadvantages of the priorart are overcome and alleviated by the present thermoplastic pallet. Thepresently disclosed thermoplastic pallet advantageously incorporatesfire resistance, while retaining durability, low weight and low cost.Such fire resistance is gained by virtue of one or more of the followingaspects: a sprinkler friendly deck or frame; variable fire retardant orcoating distributions; fire collapsible cross beams; foam filled or foamcoated parts; and pallet design, including proportioning amounts ofplastic and metal utilized in construction. Exemplary combinations offeatures enables the pallet to meet all the dimensional, mechanicalbehavior and burn test requirements. The use of metal componentsincluding a corrugated aluminum deck having specially position throughholes for sprinkler water, and the engineered placement of hollows inthe structural plastic parts enables a reduction in the amount ofplastic, and the amount of fire retardant in what plastic there is andin the pallet as a whole.

The above-described and other features will be appreciated andunderstood by those skilled in the art from the following detaileddescription, drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the accompanying FIGURES, which are meant to beexemplary and not limiting:

FIG. 1 is a semi-schematic elevation view illustrating pallets stored ona rack in a warehouse having sprinklers;

FIG. 2 is a partial vertical cross-sectional view of an exemplary palletincluding corrugations having holes;

FIG. 3 is a perspective cutaway view of an exemplary pallet includingcorrugations having holes;

FIG. 4 is a perspective cutaway view of an exemplary pallet havinginterconnected corrugations having holes;

FIG. 5 is a perspective cutaway view of an exemplary pallet havingcorrugations interconnected with an angled deck supporting frame havingholes;

FIG. 6 is a partial vertical cross-sectional view of an exemplary pallethaving contoured base portions;

FIG. 7 is a partial vertical cross-sectional view of another exemplarypallet having contoured base portions;

FIG. 8 is a partial vertical cross-sectional view of another exemplarypallet having contoured base portions;

FIG. 9 is a cross sectional view of an exemplary pallet;

FIG. 10 is a cross sectional view of an exemplary pallet column;

FIG. 11 is a cross sectional view of an exemplary pallet column anddeck;

FIG. 12 is a cross sectional view of an exemplary pallet corner;

FIG. 13 is a cross sectional view of an exemplary pallet deck;

FIG. 14 is a cross sectional view of an exemplary pallet component mold;

FIG. 15 shows a bottom side of an exemplary plastic pallet having anarray of beams which are embedded in the bottom of the pallet;

FIG. 16 shows a detail of the top cross section view of an exemplarypallet corner;

FIG. 17 is a vertical elevation end view of exemplary pallet supportedin a warehouse rack along its opposing lengthwise ends;

FIG. 18 is a front elevation view of an exemplary beam incorporated in apallet;

FIG. 19 is a bottom view of a pallet incorporating a plurality ofexemplary beams;

FIG. 20 is a bottom view of a pallet incorporating a plurality ofexemplary beams;

FIG. 21 is a bottom view of a pallet incorporating a plurlity ofexemplary beams;

FIG. 22 is a cross sectional view of an exemplary tubular beam andconnector;

FIG. 23 is a cross sectional view of an exemplary tubular beamconstruction;

FIG. 24 is a partial cross sectional view of an exemplary pallet columnincorporating a foam therein;

FIG. 25 is a partial cross sectional view of exemplary foam filledpallet deck and columns;

FIG. 26 is a cross sectional view of an exemplary pallet I-beamincluding a foam; and

FIG. 27 is a partial perspective view of an exemplary fire resistantpallet.

DETAILED DESCRIPTION

The presently disclosed thermoplastic pallet advantageously incorporatesfire resistance, while retaining durability, low weight and low cost.Such fire resistance is gained by virtue of one or more of the followingaspects: a sprinkler friendly deck or frame; variable fire retardant orcoating distributions; fire collapsible cross beams; foam filled or foamcoated parts; and pallet design, including proportioning amounts ofplastic and metal utilized in construction. Sprinkler friendly decks orframes are described with regard to FIGS. 1-8. Variable fire retardantor coating distributions are described with regard to FIGS. 9-14. Firecollapsible cross beams are described with regard to FIGS. 15-23. Foamfilled or foam coated parts are described with regard to FIGS. 24-26.

Referring now to FIG. 1, a semi-schematic elevation view illustratespallets stored on a rack in a warehouse having sprinklers. Pallets 20Care illustrated as provided singly, stacked, and loaded with goods 24,wherein the pallets are stored on racks 22 which comprise opposing sidecolumns 22L and 22R and horizontal rails 34 which are spaced apart toreceive the opposing edges of the pallets. The ceiling 30 of thewarehouse is fitted with a firewater plumbing system comprisingpressurized water pipes 28 and sprinkler heads 26. For typical sprinklerheads, when the ceiling temperature rises above a predetermined designpoint, established by selection of a low melting point metal thatrestrains a spring-loaded water valve, the sprinkler heads open anddischarge a volume of water W in the form of sprays 32. The spray waterfalls generally downwardly, to land on the stored pallets below. The aimis to cool the burning objects below the point of ignition, and toprevent non-burning objects from rising to such point.

Referring now to FIG. 2, as illustrated by the partial vertical crosssection of a pallet 20, the pallet deck 46 of an exemplary pallet 20 iscorrugated for strength. Through-holes 40 receive water W within thevalleys 45 of corrugations and pass water W to structures 44C below thepallet deck 46, thus cooling those structures below. The edge of apallet 20 rests on the rail 34 of a rack 22L. It is to be understoodthat the term corrugation or corrugated should encompass any surfacetopography that includes at least one channel, groove, depression orvalley along which water can be channeled or contained. Additionally,the base of the pallet includes any portions of the pallet below the topsurface of the pallet, which top surface may include the deck and thetop portions of the frame.

Referring now to FIG. 3, exemplary pallet deck 46, which may comprisemetal, metal alloy, plastic or other material, is attached torectangular plastic frame 48 of pallet 20. The frame 48 is mounted oncolumns 42, 42C which run down to the base comprising outer rails 44shaped as a rectangle and cross rails 44C which run to and from themidpoints of rails 44, crossing at center column 42C. Metal beams, notshown, or other reinforcing components may be provided within the railsand frame 48 for strength as in U.S. Pat. No. 6,705,347, the disclosureof which is incorporated herein by reference. As in FIG. 2, theexemplary pallet deck 46 has a multiplicity of corrugations for strengthwhich comprise depressions or valleys 45.

With reference to FIGS. 2 and 3, through-holes 40 are located at thebottom of valleys 45 of the deck. The holes are selectively located overthe rails 44C or whatever other structure comprises a lower portion ofthe pallet. There may be other holes which are not above rails or otherbottom structure, for drainage. For instance, if there is a corrugationdepression which does not lie above a rail, that corrugation could befitted with a hole.

Thus, at least part of the water W which lands on the pallet during afire, either from sprinklers, or from another pallet stacked above,flows through the specially-positioned holes 40, so the water lands on athermoplastic rails 44C or other structure which comprise the base ofthe pallet, to suppress or prevent burning. Improved performance hasbeen seen in the aforementioned Underwriter Laboratories tests. Should apallet have a continuous bottom deck construction, then holes canlikewise be placed in the bottom deck. The valleys 45 may be slopedslightly along their length, so water runs downwardly toward the holes40.

With reference to FIG. 4, another exemplary embodiment is illustrated at20A. At least some of the corrugations of the deck are connected byconnector channels 50, to help distribute the water amongst thedifferent valleys 45. Such configuration tends to even water flow intoholes 40, when the water falls unevenly on the surface of the deck. Theconnectors 50 may also be staggered from valley to valley, for best deckstrength.

Referring now to FIG. 5, part of an exemplary corner of a pallet isillustrated. In one exemplary embodiment, frame 48A, which supports deck46, has through holes 52, which are configured to drop water on theouter rails 44 of the base. In another exemplary embodiment, the topsurface of the outer part of the frame is sloped inwardly toward thecenter at slight angle Z. In such embodiment, water falling on outerportions of said deck supporting frame will tend to run to innerportions of said deck supporting frame. The top surface of the frame mayalso provide a gutter 60, so water will flow lengthwise along the frame,as suggested by the arrows. Water flows to the locations of holes 52which are positioned above base rails 44, as they run between thecolumns. The water drops onto the base rail 44, and from there onto anypallet below. Thus water which lands on, or flows over typical framesurface portion 56, which is over the corner column 42 (not shown inFIG. 5), is usefully directed onto the base or other lower portions ofthe pallet. In addition, peripheral connector channels 58 may be used toallow water in some of the valleys 45 to flow onto the top of the frameand into the gutter.

In other exemplary embodiments, the top surface of rails 44, 44C may beusefully shaped to help fire resistance. Referring now to FIG. 6, rail44A is provided with a slope, which directs water towards internalportions of the pallet or ensures that water will flow through lowerportions of the pallet to goods or additional pallets below, rather thanallowing water to possibly flow outward, as when the rail 44 a is flator fully crowned. Referring now to FIG. 7, exemplary rail 44B has asurface which is concave or grooved, such that water flows through holes62 provided in lower portions of rail 44B and onto goods or additionalpallets below, rather than allowing water to possibly flow outward.Similarly, FIG. 8 illustrates an exemplary rail 44E having a corrugatedsurface for the similar purpose. Such base portion surface contouring,which contouring selectively directs water, may similarly be applied tobase portions provided underneath holes in said deck.

It should be noted that the perforations in the deck and other parts ofthe pallet need not be round. For example, slots, among otherconfigurations, may be used. At any location, more than one hole may beplaced. The holes may also be of various sizes. As should be evident,the different features described can be combined with each other. Palletmaterials may comprise plastics, metals, wood, and the like, as well ascombinations of the foregoing.

Accordingly, the present disclosure provides, in part, a water flowcontrol system for a pallet, which selectively directs water depositedon upper surfaces of a pallet by fire sprinkler systems to lowerportions of the pallet that may gain additional fire resistance fromexposure to such water.

Solid particulate fire retardants may also be included in thethermoplastic pallet compositions, for example Grafguard graphiteintumescent material, aluminum trihydrate, magnesium hydroxide orantimony trioxide (often used with bromine compounds), among others. Thesolid fire retardants may be used in combination with other types offire retardants, for instance, brominated hydrocarbons. It will beappreciated that the invention may be applied to the inclusion of otheringredients, solid particulate or not, in a pallet and to otherarticles.

The present invention also recognizes that addition of fire retardantsin quantities sufficient to impart minimal to good fire resistance,which in one embodiment, and depending on the material, ranges from 10to 30 weight percent retardant, correspondingly decreases the fracturetoughness of that article. In the example of plastic pallets, the palletbecomes too prone to breakage, particularly around the edges of thepallet where the shanks of the tines of a forklift truck may impact thepallet. Accordingly, an improved article is described, wherein fireresistance of the article is selectively tailored with regard to thegeometry and/or position of a component of the article.

Referring now to FIGS. 9-13, partial vertical cross sections of portionsof exemplary thermoplastic pallets are illustrated. Referring to FIG. 9,exemplary pallet 220 comprises a deck 222, which is welded to thecolumns 226 of base 224. In this exemplary embodiment, the deck includesa plurality of holes (the deck may take other configurations, e.g.,solid or grid-like, among others). The columns 226, which have hollowsat their top ends, are interconnected by rails 230. Hollow square crosssection metal beams 228 are within the rails. In one exemplaryembodiment, deck 222 of pallet 220 has a higher concentration ofretardant relative to the frame 224. As an example, HDPE deck has 10%intumescent composition, and the frame has 5%. (All concentrations areby weight unless otherwise indicated.)

Referring now to FIG. 10, a portion of exemplary pallet 222A isillustrated, wherein beam 228 is covered by a floor plate 229. In anexemplary embodiment, the plate 229 is configured to incorporate of thebeam 228 within the base and comprises no or low fire retardant relativeto other portions of the pallet. In such embodiment, the beam 228 isstrategically engineered to fail in the event of a fire. This is due tothe lack of significant fire retardant in the plate 229. At an earlystage in a fire, the beam 228 will be subjected to heat and will failaccording to engineered design.

Referring now to FIG. 11, an exemplary pallet 220B is illustrated,wherein such pallet lacks base rails. An exemplary deck is a two-layercomposite structure, which may be made for example by co-extrusion, byjoining one sheet to another, or by injection molding, among othermethods. In one embodiment, the underside layer 227 comprises a firstcomposition with a large amount of fire retardant relative to the toplayer 225. Such exemplary configuration provides durability for the topof the deck, but at the same time provides fire protection to the pallet(oftentimes flames will rise up from below, and the lower deck layerprovides a lower barrier relative to heat sources from above as well).Other layers may also be interposed between the top and bottom layers,for other properties or fire resistance. The layers may also becontoured to create cavities therebetween, and the cavities may befilled with foam, such as urethane.

Referring now to FIG. 12, opposing edges of an exemplary pallet 220D isillustrated, wherein deck 222D has an inner portion comprising a firstmaterial having fire retardant (and thus diminished impact or otherproperties) and an integral edge portion 242 with less fire retardantand better impact properties. In another exemplary embodiment, the edgeportion that has minimal or no fire retardant at least spans theopenings that are between columns 226D, through which forks enter thespace under the pallet for transport.

Referring not to FIG. 13, a top view of exemplary pallet 220C isillustrated, wherein deck 222C has a central area 234 with higherretardant content than a periphery portion 232. The dashed boundary line233 is one exemplary indication of where the composition changes.Depending on the manufacturing technique that is used, and theobjective, the demarcation of composition change may be definite orgradual. While the periphery of the deck may be thin and thus shouldhave fire retardant in accord with another teaching herein, the volumeof plastic, which has the inferior fire retardant, is a small fractionof the total pallet. Thus, while burn test performance might be somewhatreduced the performance can still be acceptable, and the “give up” iswell traded against durability and strength, in considering the totalpallet design.

It is noted that rather than varying the pallet composition, a fireresistant or reflective coating may be applied to portions of thepallet. In another exemplary embodiment, part or all of the palletsurface is coated with a heat reflective material. Additionally,selected under-side exposed surfaces of the pallet may be coated withthe heat reflective surface. In an exemplary embodiment, a thin layer ofaluminum or other shiny metal is vapor deposited, using well knowtechnology, on the selected surfaces of the plastic. Alternately,aluminum metal foil can be adhered to the surface of the plastic. Thus,the amount of thermal radiation received from adjacent pallets or othermaterials which may be burning is reduced. The time for the coatedpallet portion to rise in temperature and ignite is increased, resultingin improved fire-resisting characteristic.

Referring now to FIG. 14, a simplified cross section view of anexemplary mold for a pallet other dual property object is illustrated.The exemplary cavity parts 226CC, 232CC and 234CC are illustrated ascorresponding to numeral parts of exemplary pallet 220C. The moldcomprises two mating parts 236, 238. When installed in a moldingmachine, injection mold nozzles feed molten plastic through ports 254,256. Two different material compositions, one with high retardantcontent, the other with low or no retardant content are provided by twodifferent sets of nozzles, fed by appropriate injection extruders andsupplies. The low content material is injected in the ports 254 whilethe high content material is injected in the ports 256. In anotherexemplary manufacturing alternative, with reference to FIG. 13, the deckparts 234, 232 may be separately fabricated and then joined together, asby welding.

The presently disclosed pallet recognizes that when there is a warehousefire involving molded plastic pallets which are stacked one aboveanother in a warehouse rack, the rate of heat output will be mitigatedif the surface area of plastic pallet material which is exposed toflames is reduced. Thus, as described by exemplary embodiments herein, apallet subjected to the heat of a fire desirably fails and falls fromthe rack. Such pallet may fall onto an underlying pallet and goods, oronto the floor. When multiple pallets sandwich together, the exposedsurface area of burnable material will be reduced, and the access ofoxygen bearing atmosphere is inhibited.

Referring now to FIG. 15, a bottom side of an exemplary plastic pallet120 is illustrated, wherein an array of beams is embedded in the bottomof the pallet. Without being limited, pallet 120 may be constructed inaccord with the aforementioned commonly owned U.S. Pat. No. 6,705,237 toMoore et al., the disclosure of which is hereby incorporated byreference. The embedded beams are represented in this and other figuresby dashed lines.

Referring still to FIG. 15, the exemplary beam array compriseslengthwise beams 124 and cross beams 126. (Length and width arearbitrary in this disclosure, except that a pallet is considered tomount in a rack with its length parallel to the rails 130 of the rack.)In one embodiment, the beams are perforated steel box beams. In anotherexemplary embodiment, the beams run around the rectangular periphery ofthe pallet. In another exemplary embodiment, the beam ends are close toeach other, but the beams are not structurally attached to each other.

Referring now to FIG. 16, a detail of the top cross section view of anexemplary pallet corner is illustrated. The beams cross in the center ofthe pallet. The beams may be in the base and top frame of the pallet andare generally parallel to the plane of the pallet, that is to the planeof the goods-carrying deck 134 at the top of the pallet.

In one exemplary embodiment, the pallet has a metal deck. In suchembodiment, beams are provided in the rails which comprise the base ofthe pallet. While the above describes exemplary metal reinforcing beams,beams made of other materials, for example composite plastic materials,such as graphite reinforced plastic, or some strong ceramic, may beused. The beam is, in general terms, a member, partially or fullysurrounded by the thermoplastic of the pallet (though not necessarilyembedded therein), having substantially different properties, inparticular, higher elastic modulus and tensile strength.

Referring now to FIG. 17, a vertical elevation end view of exemplarypallet 120 is illustrated as supported in a warehouse rack along itsopposing lengthwise ends 136. The opposing sides 136 of the pallet reston opposing side lips of L-shape cross section rails 130 of an exemplarypallet storage rack. Without being limiting, the distance between theinner edges of the racks, RL, is typically about 42 inches, to receive atypical pallet which is 48 inches wide.

Referring still to FIG. 17, in another exemplary embodiment, the crossbeams 126 have a length LB which is less than the spacing RL between therails, and the beams are centered between the opposing lengthwise sides136. Thus, there is a gap G between the vertical extension of the endsof the beams and the vertical extension of the inner edges of the lipsof the pallet rack. As used herein, a beam which is shorter than thewidth between the rack edges is called a “short beam”. Of course, thereis some clearance between the vertical sides of the rails of the rackand the outside edges of the pallet. Thus, in another exemplaryembodiment, the lengths of beams 126 are sufficiently short toaccommodate the resultant play or possible shifting from side to side ofa pallet mounted in the rack. Thus, in all cases with regard to thisexemplary embodiment, the end of a beam 126 will not be above thevertical extension of the innermost edge of the rail. In other exemplaryembodiments, e.g., where one end may extend beyond said verticalextension, and the other does not, the length and/or position of thebeams may chosen accordingly to anticipate shifting within the rack.

In accordance with the above exemplary embodiments, in the event of afire, the plastic of the pallet softens and loses strength, and or burnsaway, and cross beam 126 will no longer be supported at one or both ofits ends. As the plastic softens or disappears, the one end of thepallet will fall from the rail, and the pallet will collapse into thespace between the rails.

Referring now to FIG. 20, in another exemplary embodiment, at least onebeam 26A is offset (although all beams may be) from one lengthwise edgeso that one end of the beam is vertically above the rack rail, but theother end is not. In this exemplary embodiment, the cross beams may beshort beams, or they may have lengths which are equal or greater thanthe space between the rail inner edges.

As illustrated in FIG. 15, lengthwise beams 124 run generally parallelto the rails and generally transverse to the cross beams. Lengthwisebeams 124 need not have the features of the cross beams. Of course, ifthe pallet is intended also for mounting in racks which hold the palletcross-wise, then beams 124 may have the same features as are describedfor cross beams 126. In a pallet having the desired cross beam featuresdescribed herein, beams 124 may be displaced inwardly relative to theedges of the rails of the rack, as for example, shown in FIG. 18 andFIG. 21. Because, in this exemplary embodiment, the lengthwise beams arenot structurally attached to the cross beams, the engineered palletworks even when both lengthwise beams lie vertically above the rack railwhen the pallet is stored.

Referring now to FIGS. 19-21, exemplary beam configurations areillustrated. FIG. 19 illustrates an exemplary configuration whereinbeams 126 overlie one cross rail 30, but not another.

FIG. 20 illustrates an exemplary embodiment wherein cross beams 126 arestaggered in their offset. Beams 126A are offset to the right, and beam126B is offset to the left. So, in use two of the beam ends at one sideof the pallet have a gap G3 relative to the rail 130L, while the otherbeam end has a gap G4 relative to rail 130R.

FIG. 21 illustrates an exemplary embodiment wherein cross beams 126 areall offset to one side of the pallet. That is, the ends are farther fromone side than from the other side. Thus, in use all the beam ends willbe farther from the rail 130L than from rail 130R. Lengthwise beams 124are also incorporated into the pallet.

In certain exemplary embodiments, at least one cross beam incorporatesthe features described. If a pallet has a beam which fully spans thespace between the opposing sides of the rack, when one or more of theother beams are configured as described above, in a fire, the pallet canbe sufficiently weakened by the loss of support of the short or offsetbeams, such that it will tip around the one or more full length beams.

Referring now to FIG. 22, another exemplary embodiment, incorporates ametal cross beam 126D made of two pieces joined by a press-fitthermoplastic connector 132. In another exemplary embodiment, theconnector is offset from the center of the beam length, so it is notunder a column. In such embodiment, there will be less mass of plasticto provide thermal inertia and inhibit heating and softening during afire. The plastic of the connector may have the same or differentproperties, as compared to the plastic of the pallet. When there is afire, the plastic of the connector 132 melts and fails, under thestresses imposed by the pallet weight and whatever load is on thepallet, and the pallet collapses. In this embodiment and the followingtwo embodiments, the lengths of the cross beams may be short or ofregular length.

As mentioned above, the beam need not be a metal material, but maycomprise other materials. In another exemplary embodiment, a beam ismade of composite plastic material, for instance a strong fiberreinforcement, which beam in incorporated into a less strong matrix ormolding compound. The matrix is chosen so that it deteriorates whenheated, so that the reinforcing material can no longer serve its purposeand the beam collapses. For example, the beam may comprise long strandglass fibers or graphite fibers contained in a thermoplastic matrixwhich may or may not be different from the thermoplastic material of thepallet. The matrix softens and yields when there is a fire. Thus, thefibers will be no longer firmly gripped, relative to one another. Thebeam then loses its structural modulus, its shape, and its loadcapacity, and it and the pallet collapse. As an example, thereinforcement may be glass or graphite or metal fiber and the matrix maybe high density polyethylene HDPE, polypropylene PP, polysufone PSF,polyethersulfone PES, or analogous material

In another exemplary embodiment, the beam comprises lamellae, such asstrips of sheet metal or strands of wire. For example, the cross sectionof FIG. 23 shows tubular beam 126F, comprising shaped pieces of lightmetal angles 134, held together using a thermoplastic or other heatdegradable adhesive, or an injected encapsulating layer, as suggested bythe dashed line 136 in the Figure. In a fire, the adhesive fails and thebeams fails. While softening is the likely intentional failure mode ofthe plastics and matrixes here, other modes of failure due to heatingmay ensue.

In certain exemplary embodiments, the beam is described as embedded inplastic. It should also be recognized that simply placing the beam nearsuch plastic may be sufficient, as long as melting of the plastic causesthe beam to fail or displace. For example, suitable arrangements includeplacing the beam in a slot, wherein the beam may be partially exposed.Particularly for those embodiments which used a composite structurebeam, there may be openings or thinner sections in the plastic aroundthe beam, to speed localized heating and weakening of the beam during afire.

The principles of the invention may also be applied to other productswhere there is a static load or dynamic load on the product and thestructure desirably loses its strength in event of a fire or otherthermal excursion.

In another exemplary aspect, the presently described thermoplasticpallet includes a foam material, which material by composition andplacement, impart fire-resistant to the thermoplastic pallet. By“fire-resistant”, as described herein, it is meant that the pallet has adesirable combination of properties, including ignition, burning rate,heat release rate, and retention of structural strength, as such areobserved when the pallet is subjected to standard and non-standard firetest conditions. For example, the presently described thermoplasticpallet will generate energy at a lower rate than such pallet wouldotherwise generate.

A unique plastic pallet design comprising metal reinforcing bars andother special features, to provide efficient design, and to givestrength to a pallet under normal and elevated temperature conditions isdescribed in copending U.S. patent application Ser. No. 10/729,615. Thepallet comprises several structural polymer or metal elements that areassembled and then joined together. In an exemplary embodiment, thepallet structure is made of polypropylene (PP) or high densitypolyethylene (HDPE). The pallet may have metal pieces as strengtheningbeams and a corrugated aluminum deck. The assembly nature of palletdesign makes it convenient to have portions with differing materialproperties.

However, it is noted that in tests, the polyolefin thermoplastics, andin particular common HDPE and PP have poor fire resisting properties. Bytheir nature they lose rigidity and structural strength, and they meltand can form puddles of burning plastic, when subjected to fire. Themetal deck helps in providing strength during burning, and the metaldeck, compared to a plastic deck, reduces the rate of heat release.

When there are structural sections of plastic, they may be in crosssections which approximate the cross section shape of I, H, C, O, etc.,as appropriate, rather than being made solid, in accord with good designto lighten weight and keep down the cost of polymer and the pallet.Thus, a monolithic polymer beam may be made in the above-described crosssection shape. Lightening holes or analogous filigree structure may beused in selected areas, such as in the web of an I beam.

The pallet component shapes may be complex, but approximations of thosevarious features are used. However, insofar as fire resistance isconcerned, these approaches also have the undesirable effect ofproviding a greater surface area of the plastic member when it partiallyburns through, and that enhances the propensity for burning in anoxidizing environment. The present application provides a good solutionto those undesirable effects by selective application of foam to thesestructural components.

Referring now to FIG. 24, a vertical cross section through a plane, justoff the center of an exemplary pallet is illustrated. As illustrated,the exemplary pallet 320 has a base 36 comprising of cross rails havinginternal metal beams 326A, 326B, and columns 334 running up from thebase (exemplary column 334 is illustrated as positioned at an outer edge324 of pallet 320), which support a rectangular frame 338, havinginternal metal beam 326T. A corrugated metal deck 322 is mounted in theframe 338. It should be noted that exemplary components are shown insimplified and conceptual manner. The beams 326A, 326B, 326T arecontained within solid plastic sections. In an exemplary embodiment, thestructural components also include hollows. More particularly, the outerportion of the frame 338 and the columns (of which in one exemplaryembodiment, there are eight around the periphery and one in the center)may be hollow. The hollows 330 of the columns are illustrated aspartially or fully filled with foam, which in one embodiment may be asemi-rigid closed cell polyurethane foam. Depending on the nature of thehollows in the frame (with regard, e.g., to design for impactresistance, etc.), and manufacturing limitations, hollows 332 in theframe may or may not be filled with foam.

Referring now to FIG. 25, another simplified and exemplary configurationof pallet 320A is illustrated, wherein the deck 322A and columns (orfeet) 334 are comprise hollow structural plastic. A foam is providedwithin the hollow portions of the deck 322A and columns 334. It shouldbe noted that filling the hollow portions of the pallet with semi-rigidfoam may provide increase in bending or column strength (particularlywith regard to the present embodiment). Also, a significant increase inimpact strength may be achieved.

Any of the foam described herein may optionally include fire retardants(it being understood that the presently described structural componentsincluding faom are beneficial without flame retardants). That result canbe attributable to the fact that when the foam is confined within thestructural plastic which defines the portion of the pallet, the portionacts largely as it would if it were solid. The foam tends not to meltwhen burning to the extent that the structural plastic would. And ofcourse, being largely void, it has less mass. Furthermore it isinsulative. Second, if there is burn-through of the structural exterior,the fire spreads less slowly in the interior because the foam inhibitsoxygen and heat from reaching the other interior surfaces of thestructure. Thus, the rate of burning and heat evolution of a hollowstructural element is thus inhibited by putting foam inside of a hollowarticle. The amount of foam can also be varied along the length of amember, so that a controlled collapse of the pallet can be achieved,where it may be desirable to collapse part or all of a burning pallet toreduce exposed surface area and consequently reduce the amount of palletburn.

In one exemplary embodiment of the invention, a hollow structure of HDPEor PE (for example the column 334 of FIG. 24), having a wall thicknessof 0.050 to 0.200 inch, is filled Class I polyurethane foam having adensity of 2 to 4 lbs per cubic foot (for example, such as is suppliedby BASF, Livonia, Mich.). The foam may completely or partially fill thehollow portions and/or may cover the exterior.

If a fire retarding additive is used in the foam, an exemplary materialis Grafguard intumescent graphite material. The fire retarding additivemay be mixed into the the polymer material, e.g., polyurethane, whichwill comprise the foam before it is “shot” or injected into the hollowspaces. In one embodiment, the intumescent additive content is 5-20weight percent. Analogously with amount of foam, the amount of fireretardant can be controlled according to the burning behavior which issought. Other substances may also be incorporated into the foam, asdesired.

The foam which is used will provide a thermoplastic section of thepallet with improved burn test heat release characteristic; andpreferably improved impact strength. When a structural element isexposed to fire generally, or ignited at one end, the rate of burning isdecreased compared to when foam is not used. Where there is foam, it isfirst of all insulative. Second, its character upon burning, that itremains substantially in place inhibits oxygen and heat from reachingthe surface of the HDPE structural element. Thus, when there is a hollowelement filled with foam, even though part of the skin burns away, sayat the first end which is ignited, the flame will only progressaccording to the oxygen which reaches the element on its unprotectedexterior, since the interior foam greatly inhibits such on the interior.Thus, the element, and the article as a whole, is found to burn moreslowly, which means its rate of heat release is desirably less, infulfillment of meeting the aims of the UL Standard. Likewise, astructure which heats and burns more slowly will retain its structuralstrength for a longer time. Other foam materials, and other porousmaterials, known in the art which behave as described may bealternatively used in substitution of a thermoset foam or in combinationwith it. For example, ceramic or glass or expanded mineral foams may beused as fillers within a thermoset or other foam, or by themselves.

In another exemplary embodiment, a molded column 334 of a pallet, havingexemplary dimensions of 8×5×6 inches, is filled with foam. The foam maybe placed within the hollow sections by injection after the pallet isformed, including by use of the techniques where nubs or feet seal theholes of injection at the bottom of a pallet column.

Referring now to FIG. 26, another exemplary embodiment illustrates athermoplastic structural element comprising an I-beam section 330 thatis partially or fully covered with foam 342. In one exemplaryembodiment, the foam is a low density polyurethane foam (or othercomposition foam exhibiting comparable properties) adhered to thesurface of the structural element. The foam on the exterior may besomewhat less effective than filled interior embodiments, and the foammay be susceptible to mechanical damage, but a significant benefit inburning characteristic is still realized. As noted above, foam may alsobe placed on the interior and exterior of a hollow member.

It should be apparent that to the extent inclusion of a fire retardantchemical is economic, does not significantly raise weight, and isotherwise acceptable, it may be included in the foam and will likelyenhance performance of the foam.

Referring now to FIG. 27, an exemplary combination of certain fireresistant features is illustrated. FIG. 27 shows a 40×48 inch pallet420, to illustrate the exemplary features of the invention. Pallet 420has a rectangular base 422 and top 424. The base comprises peripheralrails 428 and cross rails 430. A multiplicity of integral columns 436(e.g., nine) run upwardly from the base to support the top. There aresteel beams 430 within the rails. The columns have hollows 434 which arefilled with polyurethane thermoset foam. Top 424 is comprised ofrectangular plastic frame 434, which has selectively placed hollows orvoids 436, e.g. in the spans between the columns. Metal deck 432,preferably made of corrugated aluminum sheet with drain holeperforations, is supported by and attached to the frame.

The top cooperates with the structure of the base and columns, toprovide requisite strength to the pallet. Since the top is in goodfraction aluminum sheet which does not burn readily in a fire test, theamount of plastic in the pallet is reduced. The base has metal beamswhich are configured for controlled collapse in a fire. The columns havehollows as does the periphery of the frame has voids or hollows. Thoseand the metal beams, as well as the structural strength of the metaldeck, cooperate to reduce the amount of structural plastic in the palletwithout compromising structural performance. While thermoset foam burns,it burns at a lower rate than structural thermoplastic. Since the amountof plastic in the whole pallet is reduced, compared to a pallet withoutthe metal parts and without any interior hollows or foam, the amount ofheat release from a pallet during a test is reduced. Since the pallet islight, it reduces the amount of thermoplastic and or fire retardant inthe pallet. Limiting the amount of fire retardant in a pallet helpskeeps the weight within limits and helps costs.

The pallet of the present invention is by weight about 50-70 percentthermoplastic having flame retardant; and about 30-50 percent metal. Inan exemplary polypropylene pallet, the total weight is about 55 pounds,the aluminum deck weighs about 6 lb (11-12%), and the steel reinforcingbeams weigh about 12.5 lb (23-25%).

In burn tests, a comparable dimensioned and structural strength pallet,which metal beams, but which had neither the metal deck nor drain holesnor thermoset foam of the present invention, performed in a far inferiormanner to the present invention, when the thermoplastic and fireretardant were the same. Thus, that demonstrates that for a comparablestructural performance, the invention features just mentioned enable theplastic to have fire retardant. That enables better properties or lesscostly raw materials of additives.

While exemplary embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. It is to be understood thatthe present invention has been described by way of illustration and notlimitation.

1. A fire resistant thermoplastic pallet; comprising: a pallet decksupported over a pallet base, wherein at least one of said deck and basecomprise a thermoplastic material configured to be fire resistant byvirtue of two or more of: fire sprinkler water holes provided therein,variable fire retardant or coating distributions, fire collapsiblecomponents, and foam filled or foam coated parts
 2. A fire resistantthermoplastic pallet in accordance with claim 1, further comprising acorrugated deck supported over a base, the deck having at least one holein a valley of a corrugation, wherein the flow area of said at least onehole is located over a part of the base of the pallet.
 3. A fireresistant thermoplastic pallet in accordance with claim 2, wherein whensaid pallet rests on a level surface, said at least one hole is locatedin a lower region of said corrugation, such that water landing inanother portion of said corrugation will tend by gravity to run towardsthe portion of said corrugation containing said hole.
 4. A fireresistant thermoplastic pallet in accordance with claim 2, wherein aplurality of corrugations are interconnected.
 5. A fire resistantthermoplastic pallet in accordance with claim 4, wherein said pluralityof corrugations are interconnected via staggered channels.
 6. A fireresistant thermoplastic pallet in accordance with claim 2, wherein whensaid pallet rests on a level surface, an outer length of said decksupporting frame is either higher than a hole in said deck supportingframe or higher than said deck, such that water will tend to flow towardsaid hole or toward said deck from said outer length of said decksupporting frame rather than flowing over the outer length of said decksupporting frame.
 7. A fire resistant thermoplastic pallet in accordancewith claim 6, wherein said deck supporting frame includes a plurality ofholes, which holes are provided in portions of said deck supportingframe that are lower than an outer length of said deck supporting frameand lower than portions of said deck, such that water will tend tocollect or flow between said plurality of holes in said deck supportingframe.
 8. A fire resistant thermoplastic pallet in accordance with claim1, comprising a plurality of thermoplastic portions, wherein at leasttwo of said portions have differential fire resistance, by virtue ofcompositions or coatings, according to the position or geometry of saidportions.
 9. A fire resistant thermoplastic pallet in accordance withclaim 8, wherein wherein at least one said portion is thinner or has ahigher surface area to volume ratio relative to another of saidportions.
 10. A fire resistant thermoplastic pallet in accordance withclaim 8, wherein a deck of the pallet has higher fire retardant contentthan columns upon which the deck is mounted.
 11. A fire resistantthermoplastic pallet in accordance with claim 8, wherein part or all ofthe periphery of a deck has less retardant or no retardant, compared tothe interior of the deck which has fire retardant.
 12. A fire resistantthermoplastic pallet in accordance with claim 1, wherein the pallet isstorable in a rack having opposing side rails, by resting opposinglengthwise edges of the pallet on the rails, the pallet comprising aplastic portion configured to span the distance between the rails of therack, wherein at least one cross beam is secured on or within saidplastic portion, the cross beam and plastic portion configured such thatsaid cross beam and plastic portion will structurally fail upon exposureto heat from a fire.
 13. A fire resistant thermoplastic pallet inaccordance with claim 12, wherein said at least one cross beam has alength and location within the pallet, so that one end of the beam isconfigured such that it is inward from the lengthwise edge of the palletand inward from the vertical extension of the inner edge of the rail ofthe storage rack, and wherein, when the plastic portion softens, the endof the beam will fall downwardly from the rack.
 14. A fire resistantthermoplastic pallet in accordance with claim 12, wherein said at leastone cross beam has a length and location within the pallet, so that bothends of the beam are configured such that they inward from thelengthwise edges of the pallet and inward from the vertical extension ofthe inner edges of the rail of the storage rack, and wherein, when theplastic portion softens, an end of the beam will fall downwardly fromthe rack.
 15. A fire resistant thermoplastic pallet in accordance withclaim 12, wherein said at least one cross beam includes at least onereinforcing material engineered to degrade when exposed to heat from afire, such that the reinforcing beam will fail upon exposure to heatfrom a fire.
 16. A fire resistant thermoplastic pallet in accordancewith claim 1, comprising a thermoplastic structural pallet memberincluding a foam thereon.
 17. A fire resistant thermoplastic pallet inaccordance with claim 16, wherein the thermoplastic structural palletmember comprises polypropylene or high density polyethylene.
 18. A fireresistant thermoplastic pallet in accordance with claim 16, wherein thestructural pallet member is hollow and at least partially filled withfoam.
 19. A fire resistant thermoplastic pallet in accordance with claim18, wherein the structural pallet member is a pallet column.
 20. A fireresistant thermoplastic pallet in accordance with claim 18, wherein thestructural pallet member is a deck.
 21. A fire resistant thermoplasticpallet in accordance with claim 16, wherein the amount of foam is variedbetween different parts of the structural pallet member.
 22. A strongburn-resisting pallet, predominately composed of thermoplastic, fortransporting goods, comprising: a base, made of thermoplastic, such aspolyethylene or polypropylene, comprising rails between columns, therails having reinforcing beams within; a multiplicity of columns runningupwardly from the base; each of said multiplicity having a thermoplasticshell exterior, and filled with foam; a top, attached to the tops of thecolumns, comprising a circumscribing thermoplastic frame, mounted on thecolumns; and a metal deck, attached to and running across the interioropening of the frame; the deck having a plurality of through holes forwater drainage, so the water drops onto plastic parts of the bottom ofthe pallet and onto any pallets mounted below.
 23. A pallet inaccordance with claim 22, wherein the plastic of the rails, columns andframe contain fire retardant.
 24. A pallet in accordance with claim 22,wherein the pallet weighs no more than 55 pounds, wherein thethermoplastic material (including any additive such as fire retardant)is 70% of the weight or less.
 25. A pallet in accordance with claim 22,having a corrugated and perforated aluminum sheet metal deck whichweighs between about about 5 and 7 pounds, and steel beams weighingbetween about 12 and 13 pounds.